1 head broccoli (1 pound), cut into florets, stems thinly sliced   2 tablespoons extra-virgin olive oil   1 yellow onion, diced   2 garlic cloves, thinly sliced   One 15-ounce can cannellini beans, drained   2 1/2 cups vegetable stock   Kosher salt and freshly ground black pepper   1 tablespoon pine nuts, toasted  parmesan slivers